Disease Symptoms

Botrytis Limb Blight, or Botrytis dieback is caused by the fungal pathogen Botrytis cinerea. This pathogen can be spread by area, and is common and widespread with a large variety of hosts. Usually flowers or fruit are infected first, or shoot-tips that have been damaged by frost. The pathogen then moves from fruits or flowers into the shoots and causes the shoot to die-back.

Typically cankers are present below infected fruit, and gray spores develop on infected fruit, shoots and cankers. This pathogen can also infect young, growing shoots, entering through wounds. Infected shoots wilt, turn brown and die. Leaves or shoots may turn black under extremely wet conditions.

Conditions for Infection

This disease is most common during periods of cool and wet temperatures. Wet and cool springs favor disease development. The Pest Prophet app can be used to track weather conditions optimum for growth and development of Botrytis Cinerea, and this can be used to determine risk of botrytis infection on fig trees and can be used to optimize timing of preventative fungicide sprays.

Infected fruit may show signs of infection after harvest. If storage conditions are optimum for disease development with higher humidity and moderate temperatures, the disease can spread.

Disease Management

The most effective way to control spread of Botrytis cinerea on figs is by culling infected fruit once signs of disease are present. Similarly infected shoots should be pruned and removed from the field. Preventative fungicides can be used during cool, wet, periods, or if infection symptoms are observed in the field. Spray applications may or may not be necessary depending on history of the orchard, and severity of infection and other economic considerations.

In California, this disease is more common on caprifigs. Caprifrigs can bear early fruit that can be damaged by frost in spring, which can provide an entry point for Botrytis cinerea infection. The pathogen can also sporulate as late as July on caprifigs, which can be an additional source of inoculum.

To avoid post-harvest infection, fruit should be stored in a dry place in order to avoid growth spread of disease. Infected fruit should be culled and discarded.

Learn more: Complete Guide to Botrytis Gray Mold

Sources:

Diseases of Tropical Fruit Crops. Edited by RC Ploetz. CABI Publishing. 2003